Abstract

This paper surveys a range of numerical methods for the optimisation of material parameters in a single state-variable constitutive model applied to the hot deformation of Ti-6Sn-2Zr-4Mn-6Mo. Minimisation of an objective function, describing the least squares difference between experimental results and model output, was carried out using several methods: Nelder-Mead direct search, quasi-Newton gradient, trust-region Newton and genetic algorithms. The most robust approach involved gaining an initial estimate of parameter values using the genetic algorithms and then refining this with a Nelder-Mead search. A scheme for estimating the confidence limits of the derived parameters is also presented.